Refrigeration system with delay timing mechanism

ABSTRACT

Protection against refrigeration compressor burnout by short cycling is provided by a delay timing mechanism having a motor and solenoid. The motor is constantly energized and the solenoid controlled by a thermostat stalls or releases the mechanism causing timer operation through its cycle. The timer runs through its delay period during the normal off period, allowing fast restart of the compressor. Also the timer provides a longer delay following a short cycle then following a normal cycle. This is accomplished by operating the timer for a period of time after the compressor is started.

I Umted States Patent 51 3,640,085 Harris Feb. 8, 1972 54] REFRIGERATIONSYSTEM WITH [56] i References cm DELAY TIMING MECHANISM UNITED STATESPATENTS [721 Delafield 3,312,081 4/1967 Berger ..62/l58 [73] Assignee:Deltml Corp., Bellwood, Ill. 3,434,028 3/1969 McCready.... ...3l8/484,559,4 1 L Filed: D 3 20 2/ 971 Ipscomb 62/158 [21] Appl.No 133,038Primary ExaminerMeyer Perlin Related US. Application Data [57 ABSTRACT[62] Division of Ser. No. 849,961, Aug. 14, 1969, Pat. No. Protectionagainst refrigeration compressor burnout by short 3,598,214. cycling isprovided by a delay timing mechanism having a motor and solenoid. Themotor is constantly energized and the [52] l J.S.Cl...62ll58,62/231,200/38, solenoid controlled by a thennostat stalls orreleases the 307/116, 318/484 mechanism causing timer operation throughits cycle. The [51] Int. Cl ..F25b19/00 timer runs through its delayperiod during the nonnal off [58] Field of Search ..62/ 157, 158, 231;318/484; period, allowing fast restart of the compressor. Also the timer200/38; 307/ l 16 provides a longer delay following a short cycle thenfollowing SAFETY CONTROLS a normal cycle. This is accomplished byoperating the timer for a period of time after the compressor isstarted.

9 Claims, 7 Drawing Figures STANDBY STALLED BY STANDBY STOP PATENTEUFEB81972 SHEEIIUFZ COM PRESsoR SWITCH SOLENOID RUN {STALL PATENTEI] FEB men3; 640.085

SHEET 2 BF 2 SAFETY CONTROLS 73; I HPC mi 74. 75

COMPRESSOR "commok COIL STANDBY STALLED RUNSTAL ED STANDBY BY STANDBYSTOP BY RUN STOP 7 MIN U ES 55H, I I

I I/////A WITAL l SHQQT I PRE$$URE DELAY CYCLE mp EQUALIZATION PERIODFig. 3

STANDBY PREQSURE EQUALIZATION PERIOD l Fig.4

STANDBY Fig.5

SHoRT cmi a?- EQURLIZATION PERIOD 231 3??? V//////A SW CH INVENTOR.

REFRIGERATION SYSTEM WITH DELAY TIMING MECHANISM CROSS-REFERENCE TORELATED APPLICATION This application is a division of my applicationSer. No. 849,961 filed Aug. 14, 1969, now U.S. Pat. No. 3,598,214 datedAug. 10, 1971.

BRIEF SUMMARY OF INVENTION This invention relates to automatic controlsand more particularly to timing devices for controlling and protectingcompressors in refrigeration systems.

The primary object of the invention is the provision of a compact andsimplified control system which stops and starts the refrigerationcompressor at the command of a condition responsive device and alsointerposes a delay in restarting the compressor for protecting againstoverload.

A further object of the invention is the provision of a simplifiedrefrigeration control system and control device which provides a normaldelay before restart for pressure equalization following a normal cycle,but which interposes a substantially longer delay if the compressorstoppage was due to operation of a safety control.

Another object of the invention is the provision of a device and systemproviding operation of the blower for the refrigeration system forlonger periods than the compressor is operated.

A further object of the invention is to provide a simplified timingcontrol system using an electric motor, and which operates in apredetermined cycle without requiring circuitry or switches for timermotor control.

Another object is to provide a timing device in which operation iscontrolled by selectively stalling or releasing the timer motor.

A further object is to provide a stalling mechanism in which a timingmotor is selectively stalled or released and in which the actualstalling force is removed from the mechanism controlling the stalling orreleasing.

Other objects will appear from the following description and appendedclaims.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic exploded view of amechanism embodying the invention;

FIG. la is an enlarged view of the stalling wheel of FIG. 1;

FIG. 2 is a schematic wiring diagram of a complete refrigeration controlsystem embodying the mechanism of the invention;

FIG. 3 is a chart showing the preferred operating sequence as occurs ona normal refrigeration cycle;

FIG. 4 is a chart showing a modified operating cycle;

FIG. 5 illustrates a modification of FIG. 1, and in which;

FIG. 6 is a chart showing the operating sequence provided by thearrangement of FIG. 5.

DETAILED DESCRIPTION OF INVENTION Referring now to FIG. 1, referencecharacter 1 indicates the timer motor shown schematically, this motordriving a pinion 2 meshing with gear 3 which is carried by and drives ashaft 4 which in turn drives a pinion 5. This pinion drives a final gear6 which is carried by and drives a cam shaft 7 carrying a cam 8. Thetimer motor 1 drives the final gear 6 and the cam or controller 8 in acounterclockwise direction as indicated by the arrows.

The timing means above described, through cam 8 operates a compressorswitch generally indicated as 9. This switch or control device comprisesan upper switchblade 10 and a lower switchblade 11, each anchored at itsleft-hand end and both blades being biased downwardly toward the cam 8.The lower switchblade 11 is provided with an opening 12 allowing theblade to straddle the cam 8 and providing an internal cam followersurface 13. This blade 11 carries a contact 14 and is provided with anextended portion 15 cooperating with the latch 16. The upper switchblade 10 includes a cam follower bracket 17 which extends downwardly andrides the cam 8 at a point spaced counterclockwise from the cam followersurface 13. Switchblade 10 also carries contact 18 arranged for engagingcontact 14 on switchblade 11. The cam or controller 8 consists of a maincam surface including a generally circular portion 20 and a rise portion21. The cam also includes a dropoff section 22 which causes dropping ofboth switchblades with snap action.

The latch 16 is pivoted on a shaft diagrammatically shown as 24 andincludes a latching surface 25 and a camming surface 26, these surfacescooperating with extension 15 of lower switchblade 11 as will bedescribed. The latch 16 also is provided with a biasing spring 27 whichbiases this latch toward the end 15 of the switchblade 11.

The shaft 24 which carries the latch 16 also carries a run" stallinglever 30. The latch 16 and the run staller 30 are arranged to operate inunison. While these two parts are shown as separated and spaced apartfor illustrative purposes, it will be apparent that these two parts maybe molded into a single piece thus ensuring correct alignment of theworking surfaces and lowering production cost.

The run-stalling member 30 is shown in disengaged position and isarranged to cooperate with the run-stalling lug 31 carried by the finalgear 6 to provide a mechanical stopping means. When the run stallingmember 30 is rotated counterclockwise, its stalling surface or movableabutment 32 will be brought into the path of the stalling lug 31 on thefinal gear. Thus the final gear will be stalled when it rotates to thepoint where lug 31 engages stalling surface 32. Clockwise rotation ofthe stalling member 30 takes the stalling-surface 32 out of the path ofthe stalling lug 31 and thus the timer is free to proceed beyond thispoint.

Reference character 35 indicates a solenoid lever which is pivoted at36. This lever 35 is biased in a counterclockwise direction by a spring37 and is rotated clockwise against the force of spring 37 by thesolenoid or electromagnet 38. The solenoid lever 35 includes an arm 39carrying a stalling surface 40 adapted to be engaged by a stalling lug'41 on the final gear 6 providing a mechanical stopping means. Thesolenoid lever also carries a pin 42 which isarranged to engage thesvn'tchblade 43 'of the blower switch generally-indicated as 44. Theswitchblade 43 is anchored at its left-hand end and is biased upwardly.This switchblade includes a movable contact 45 adapted to engage astationary contact 46. This switchblade is biased upwardly for causingthe contacts to engage. 'Ihe pin 42 on the solenoid lever pushes theswitchblade 43 downwardly when the solenoidis deenergized for openingsswitch 44. r

The solenoid lever 35 also carries a pin which is adapted to engage theportion 51 of the run stall member 30. This pin serves to rotate the runstall member in a clockwise direction when the solenoid is deenergized.The solenoid lever is also formed with an opening 52 through which thesupporting shaft 24 for the run stall member 30 and latch '16 passes.This serves as a stop for limiting outward travel of the solenoid lever35 and also limits the inward travelof the stalling surface40 on thislever.

The shaft 4 which carries the pinion 5 is,journaled in a spring levergenerally indicated as 55. This spring lever is pivotally supported onthe same center as the cam shaft 7 and is biased in acounterclockwisedirection by a spring 56. The amount of counterclockwisemovement is limited-bya fixed stop 57. This stop is located in a mannerto causeethe gear shaft 4 to be in alignment with the cam shaft 7 whenthespring lever 55 engages stop 57. Spring lever 55 .thus provides amovable bearing for pinion 5. The pinion 5 isrigidly attached to astalling wheel 58 having ratchetlike teeth 59 adapted to come in contactwith a-stationary stalling lug.60. The stalling lug 60 may be struckoutof the enclosure for the timing unit or mounted in any suitable manner.It is preferable that theangle of this lug at the point where engaged bythe stalling wheel be tangent to a circle centered with the shaft 7. Itis also preferable that the teeth of the stalling wheel be cut so thatthe stalling surfaces at the point of engagement with lug 60 areparallel with lug 63. The location of the stalling lug 60 relative tothe fixed stop 57 must be such as to provide clearance between thestalling wheel 58 and the stalling lug 60 when the spring lever 55 isengaging the fixed stop 57.

FIG. 2 shows the preferred complete refrigeration control systemembodying the mechanism of FIG. 1. This system includes a compressormotor 70 and a blower motor 71 which blows air across the evaporatorand/or condenser of the refrigeration system. The compressor motor iscontrolled by the usual contactor having a contactor coil C and switchesC-l and C-2 operated thereby. The system also includes a low-voltagethermostat 72, a low-voltage transformer 73 and safety controlscomprising a high-pressure cutout 74 and a low-pressure cutout 75. Thelatter controls and associated wiring comprise a means for energizingthe motor 1. The operation of the mechanism and complete system will nowbe described.

OPERATION OF FIGS 1 AND 2 With the parts in the positions shown, thesystem is in the Standby position. The timer solenoid is deenergizedwhich has the Standby stalling surface 40 in the path of lug 41 on finalgear 6. Even though the timer motor 1 is energized, no motion can takeplace as the timer is effectively stalled. The compressor switch 9 isopen and thus the compressor motor contactor C is deenergized causingthe compressor motor to be at rest. Also the blower switch 44 is openand the blower is at-rest. Assuming that the pressures within therefrigeration system are satisfactory and that switches 74 and 75 areclosed, the timer motor 1 is energized and is ready to drive the timerany time the timing mechanism is released by the stalling mechanism.When the thermostat 72 calls for cooling, it will energize the timersolenoid 38 which rotates the solenoid lever 35 about its pivot 36. Thiscloses blower switch 44 and also removes the stalling surface 40 fromthe path of the stalling lug 41 on gear 6. This in turn allows thespring 56 to rotate the spring lever 55 downwardly releasing thestalling wheel 59 from the stationary stalling lug 60. This sameclockwise rotation of solenoid lever 35 also moves the pin 50 on thislever away from the surface 51 of the stalling member 30. The stallingmember 30 however does not move into stalling position at this time asit is being held in released position by latch 16.

As the Standby stall has been released, the timer motor now drives thegear 6 and cam 8 in a counterclockwise direction. In a short time theinclined section 21 of the cam engages the cam follower surfaces 13 and17 of the switchblades 10 and 11 and starts raising the switchblades inunison with the contacts separated. As lower blade 11 is cammedupwardly, the end rides up the camming surface 26 on the latch 16allowing gradual counterclockwise rotation of the latch. When the end 15of the blade rises above the latching surface of the latch, the spring27 is free to pull the latch into complete latching position. This samecounterclockwise latching motion also causes the run-stalling member tobring its stalling surface 32 into the path of the stalling lug 31 ongear 6. Inward travel of the latch 16 and stalling member 30 is nowlimited by the surface 51 on member 30 engaging the pin 50 on thesolenoid lever 35.

As the cam 8 continues to rotate, the cam follower surface 13 onswitchblade 11 will ride down the dropoff section 22 allowing the end 15of the switchblade to rest on the latching surface 25 of latch 16 whichis now in latching position. On continued rotation of the cam 8, thefollower surface 17 on upper switchblade 10 drops off the dropoffsection 22 of the cam. Switchblade 10 now drops abruptly bringingcontact 18 into engagement with contact 14 and thus closing the loadswitch 9. This energizes the compressor contactor coil C which in turncloses its contacts C-1 and C-2 starting the compressor motor 70.

The timing mechanism will now continue to run for a predetermined timeuntil the run stall lug 31 on gear 6 engages the stalling surface 32 onthe run stall member 30 which is now in stalling position.

When the run stall member 31 engages the stalling surface 32, it stopsfurther rotation of the drive gear 6. In reaction to this, the pinion 5begins moving bodily in an upward direction, this motion being allowedby the spring lever 55 disengaging stop 57 and moving against the biasedof the spring 56. When the teeth on the staller wheel 58 engage thestalling lug 60, the timer motor is effectively stalled.

Due to the reaction-type stalling mechanism provided by the invention,the pressure required for stalling at the stalling lugs 31 or 41 is onlythat required to compress the spring 56 sufficiently to bring thestalling wheel into engagement with the stalling surface 60. Thestalling lugs 31 and 41 on the final gear are never required to stallthe full torque of the motor through the reduction gears. Instead, theactual stalling force for the motor is applied ahead of the gearreduction where the torque and force required is considerably lower.This arrangement in which the stalling force is merely triggered by thesolenoid operated surfaces makes it possible to design the timermechanism with the light duty parts and with a relatively smallsolenoid. This special stalling mechanism could be omitted, using adirect drive between the timer motor and the gear 6. However, this wouldrequire the parts being designed sufficiently strong to carry therelatively high loads, and to use a solenoid sufficiently strong toengage or release the higher stalling forces.

On a normal operating cycle, the mechanism will remain in the run stallposition with the switches 9 and 44 closed until the thermostat 72 issatisfied. When this occurs, it deenergizes the solenoid 38 causingcounterclockwise rotation of the lever 35 by spring 37. This movement ofthe solenoid lever 35 causes the pin 50 to engage surface 51 on thestalling member 30 and to rotate this member clockwise. Thissimultaneously moves the stalling surface 32 out of the path of the lug31 and also moves the latch 16 into released position allowing theswitchblade 11 to drop against cam 8 thus opening the compressor switch9. This same motion of the lever also causes pin 42 to engageswitchblade 43 and thus open the blower switch 44. Summarizing, openingof the room thermostat switch 72 deenergizes solenoid 38. This actionreleases the run-stop 30 and the latch 16 opening load switch 9 and alsoopening the blower switch 44.

The timing mechanism is now free to proceed back to the standby positionwhere lug 41 on gear 6 engages the standby stalling surface 40 onsolenoid lever 35. It is important on this point of the cycle that therun lug 31 on the gear 6 be clear of the stalling surface 40 on thelever 35. This is accomplished by limiting the inward motion of thestalling surface by a stop as provided by the edge of hole 52 in lever35 engaging the shaft 24. Any other stop arrangement may, of course, beused. The Run lug 31 on gear 6 is located inwardly sufficiently that itnever engages the Standby stalling surface 40 even when this surface isin stalling position. When the lug 41 engages surface 40, the stallingwheel 58 again engages the stalling lug 60 and stalls the timer motor 1.

It should be noted that there is only one point in the completerevolution of the timer cam where the load switch 9 can be closed. Thatis the point at which the cam follower surface 17 on switch blade 10drops off the dropoff section on the cam. In order to effect switchclosure, the latch 16 must be in place. If the latch happens to be heldreleased at this time, the load switch will remain open and it will benecessary for the cam 8 to complete another complete revolution beforethe load switch can be closed.

If during a cycle either the high-pressure switch 74 or lowpressureswitch 75 opens, it will break the circuit to the transformer 73 thusdeenergizing the solenoid 38. This will have the same effect as droppingout of the solenoid 38 by the thermostat 72 as described. In otherwords, it will open the compressor motor switch stopping the compressorand will also release the run-stop so that the timer mechanism canproceed back to the starting point. However, at this time the timermotor is deenergized as it is in circuit with the switches 74 and 75.Thus the duration of the unfavorable condition causing opening of thesafety switches is added to the delay in restarting the compressor.

FIG. 3 shows one type of operating cycle that my control may be arrangedto provide. Here the timer motor speed and gear reduction are selectedto give an overall cycle of one revolution in 7 minutes. The standby lug41 on gear 6 is located relative to the dropoff section 22 on cam 8 soas to provide a 20 second delay between energization of the solenoid 38and closure of the switch 9. The run stall lug 31 on final gear 6 islocated so as to allow a period of 2 minutes after switch closure beforethe run lug 31 engages the run-stalling surface on lever 30. This leavesa balance of 4 minutes 40 seconds that the timer must run before itreturns to the standby position in which lug 41 engages standby stallingsurface 40.

With the cycle as above described, the timer will run for a period of 2minutes after the compressor is started. Thus if the compressor runs thefull 2 minutes before stopping, there will be a delay of 5 minutesbefore the compressor can be restarted. This is the sum of the 4 minute40 second pressure equalization period plus the 20 second initial delayperiod.

If the system malfunctions and one of the safety switches 74 or 75opens, for example seconds after start, the timer must now run anadditional 1 minute 50 seconds before the compressor can be started. Inother words, the timer must now run 6 minutes 50 seconds instead of 5minutes. In addition, the timer motor is deenergized during the periodthat the safety switch remains open and this indeterminate time is addedto the delay imposed by the timer itself. Thus this system pro videssubstantially longer delays in event of malfunction than during normalcycle providing only time enough for pressure equalization.

The 2 minute short cycle adder of course, can be made substantiallylonger, even as long as the average on period of the compressor in thesystem.

FIG. 4 shows an optional cycle in which the gearing is selected toprovide a 5 minute revolution on the cam shaft. The cam is arranged togive a second delay in starting and the run lug 31 arranged to stall thetimer immediately after switch 9 closes. This gives a 4 minute 45 secondinterval for the timer to run to return to the standby position.

It will be seen that the duration of the short cycle adder can be madewhatever desired simply by selecting the proper gear reduction and bylocating the run-stall lug 31 at the proper angle on gear 6.

FIGS. 5 AND 6 In the embodiment of the invention shown in FIG. I, theblower switch 44 is opened and closed by the solenoid 38. If desired,the blower switch 44 can be held by the timer until a predeterminedperiod after the compressor is stopped. This arrangement is shown inFIG. 5 and the operation charted in FIG. 6. Here the pin 42' foroperating switch 44 is carried by a separate lever 80 which is pivotedon the same bearing 36' as the solenoid lever 35 The latch 16 and runstall member 30 are identical with FIG. 1 and are omitted from FIG. 5for reasons of clarity. The lever 80 is biased counterclockwise by aspring 81 and carries a standby-stalling surface 82 adapted to beengaged by a stalling surface 83 carried on a cam 84 located between thecam 8 and the final gear 6. A pin 85 carried by the solenoid lever 35'is arranged to engage a surface 86 on the lever 80, this pin causingclockwise rotation of the lever 80 when the lever 35' is rotated in thesame direction by energization of the solenoid.

In operation, energization of the solenoid rotates the lever 35'clockwise which lifts the lever 80 releasing the pin 42' from switch 44and also releasing the stalling surface 82 from the correspondingsurface 83 on cam 84. The cam 84 will now hold lever 80 in this positionuntil the timer rotates to the point where the dropoff portion 87 on thecam clears the cam follower surface of lever 80. At this time, thespring 81 is free to rotate the lever clockwise opening switch 44 andalso bringing the stalling surface 82 into position for stalling cam 84.

The arrangement shown in FIG. 5 has the advantage of maintaining theblower in operation in the event that the compressor is shut down byeither safety switch 74 or 75. Operation of the blower at this timehelps to remove the condition causing the shut down.

From the foregoing, it will be apparent that the invention provides anextremely simple compressor control system. Only one switch is requiredto give response to the thermostat and to provide starting of thecompressor or load. In addition, the invention provides for control ofthe blower giving blower operation both before and after the compressorrunning cycle. In addition, the invention provides for extra delay inthe event of short cycle, thus giving additional protection to thecompressor. It will also be apparent that substantial changes in theoperating cycle may be made as desired, simply by selecting thenecessary gear reduction and locating the stall lugs at the properlocations on the final gear.

While a preferred form of the invention has been shown and described,many changes may be made without departing from the spirit and scope ofthe invention as defined in the following claims.

I claim:

I. In a control system for a refrigeration system having an electricmotor driven compressor, the combination of, a condition responsivedevice, timing means including an electric timing motor for driving thesame and an electromagnet, a control circuit including the conditionresponsive device and electromagnet whereby the electromagnet iscontrolled by said condition responsive device, an energizing circuitfor the electric timing motor, said energizing circuit being independentof said condition responsive device, a switch for controlling thecompressor motor, means including the timing means and the electromagnetfor closing said switch in response to a call for condition change bythe condition responsive device, said timing means being arranged todelay closure of said switch for a predetermined minimum time, means formechanically stopping said timing means at a point providing saidminimum time, said mechanical stopping means effectively stopping thetiming means even though the electric timing motor remains energized bysaid independent energizing circuit, and means controlled by thecondition responsive device including said electromagnet for renderingthe mechanical stopping means ineffective and opening said switch whenthe condition responsive device calls for stopping the compressor.

2. The combination set forth in claim 1 in which a second conditionresponsive means breaks the energizing circuit for the electric timingmotor and also deenergizes the electromagnet in response to anunfavorable condition associated with the refrigeration system, theduration of the unfavorable condition thus being added to saidpredetermined minimum delay.

3. The combination set forth in claim 1 in which the timing meansprovides a first delay period sufficient to allow equalization ofpressure in the refrigeration system and an additional delay period inthe event of a short cycle, said mechanical stopping means beingarranged to allow operation of the timing means following starting ofthe compressor through said additional delay period and then to stopsaid timing means.

4. The combination set forth in claim 3 in which a second conditionresponsive means breaks the energizing circuit for the electric timingmotor and also deenergizes the electromagnet in response to anunfavorable condition associated with the refrigeration system, theduration of the unfavorable condition thus being added to the delayprovided by the timing means.

5. The combination set forth in claim 1 in which the refrigerationsystem includes a blower having a blower motor therefore, and a switchfor the blower motor closed by said electromagnet in response to callfor condition change by the condition responsive device.

6. In a control system for a refrigeration system having a compressorand a blower, a compressor motor for driving the compressor, a blowermotor for driving the blower, a condition responsive means, anelectromagnet, a control circuit including the condition responsivemeans and electromagnet whereby the condition responsive means controlsthe electromagnet, means including a compressor motor switch forcontrolling the compressor motor, means including a blower motor switchfor controlling the blower motor, timing means including electric motormeans, means for energizing said electric motor means, means actuated bythe electromagnet for closing the blower motor switch on call foroperation of the compressor by the condition responsive means, meansincluding the timing means for causing closure of the compressor motorswitch on call for compressor operation by said condition responsivemeans, said timing means being arranged to provide a delay betweensuccessive energizations of the compressor motor, means for stopping thetiming means at a point providing said delay, means operated by theelectromagnet on call for stopping of the compressor by the conditionresponsive means for opening the compressor motor switch, and means alsooperated by the electromagnet for rendering said stopping meansineffective, allowing the timing means to proceed with a new cycle.

7. The combination recited in claim 6 in which the blower motor switchis maintained closed by the timing means for a predetermined timefollowing stopping of the compressor motor by said electromagnet.

8. The combination recited in claim 6 in which the timing means isrestarted immediately following opening of the compressor motor switchby the electromagnet, and runs to a predetermined point, therebyshortening the delay before restart of the compressor during the timethe compressor is stopped by the condition responsive means.

9. The combination recited in claim 6 in which the blower motor switchis maintained closed by the timing means until it has run for apredetermined length of time, and in which the energization of theelectric motor means for the timing means is interrupted in response toan unfavorable operating condition associated with the refrigerationsystem.

1. In a control system for a refrigeration system having an electricmotor driven compressor, the combination of, a condition responsivedevice, timing means including an electric timing motor for driving thesame and an electromagnet, a control circuit including the conditionresponsive device and electromagnet whereby the electromagnet iscontrolled by said condition responsive device, an energizing circuitfor the electric timing motor, said energizing circuit being independentof said condition responsive device, a switch for controlling thecompressor motor, means including the timing means and the electromagnetfor closing said switch in response to a call for condition change bythe condition responsive device, said timing means being arranged todelay closure of said switch for a predetermined minimum time, means formechanically stopping said timing means at a point provIding saidminimum time, said mechanical stopping means effectively stopping thetiming means even though the electric timing motor remains energized bysaid independent energizing circuit, and means controlled by thecondition responsive device including said electromagnet for renderingthe mechanical stopping means ineffective and opening said switch whenthe condition responsive device calls for stopping the compressor. 2.The combination set forth in claim 1 in which a second conditionresponsive means breaks the energizing circuit for the electric timingmotor and also deenergizes the electromagnet in response to anunfavorable condition associated with the refrigeration system, theduration of the unfavorable condition thus being added to saidpredetermined minimum delay.
 3. The combination set forth in claim 1 inwhich the timing means provides a first delay period sufficient to allowequalization of pressure in the refrigeration system and an additionaldelay period in the event of a short cycle, said mechanical stoppingmeans being arranged to allow operation of the timing means followingstarting of the compressor through said additional delay period and thento stop said timing means.
 4. The combination set forth in claim 3 inwhich a second condition responsive means breaks the energizing circuitfor the electric timing motor and also deenergizes the electromagnet inresponse to an unfavorable condition associated with the refrigerationsystem, the duration of the unfavorable condition thus being added tothe delay provided by the timing means.
 5. The combination set forth inclaim 1 in which the refrigeration system includes a blower having ablower motor therefore, and a switch for the blower motor closed by saidelectromagnet in response to call for condition change by the conditionresponsive device.
 6. In a control system for a refrigeration systemhaving a compressor and a blower, a compressor motor for driving thecompressor, a blower motor for driving the blower, a conditionresponsive means, an electromagnet, a control circuit including thecondition responsive means and electromagnet whereby the conditionresponsive means controls the electromagnet, means including acompressor motor switch for controlling the compressor motor, meansincluding a blower motor switch for controlling the blower motor, timingmeans including electric motor means, means for energizing said electricmotor means, means actuated by the electromagnet for closing the blowermotor switch on call for operation of the compressor by the conditionresponsive means, means including the timing means for causing closureof the compressor motor switch on call for compressor operation by saidcondition responsive means, said timing means being arranged to providea delay between successive energizations of the compressor motor, meansfor stopping the timing means at a point providing said delay, meansoperated by the electromagnet on call for stopping of the compressor bythe condition responsive means for opening the compressor motor switch,and means also operated by the electromagnet for rendering said stoppingmeans ineffective, allowing the timing means to proceed with a newcycle.
 7. The combination recited in claim 6 in which the blower motorswitch is maintained closed by the timing means for a predetermined timefollowing stopping of the compressor motor by said electromagnet.
 8. Thecombination recited in claim 6 in which the timing means is restartedimmediately following opening of the compressor motor switch by theelectromagnet, and runs to a predetermined point, thereby shortening thedelay before restart of the compressor during the time the compressor isstopped by the condition responsive means.
 9. The combination recited inclaim 6 in which the blower motor switch is maintained closed by thetiming means until it has run for a predetermined length of time, and inwhich the energization of the electric motor means for the timing meansis interrupteD in response to an unfavorable operating conditionassociated with the refrigeration system.